Particulate emissions (black smoke) from diesel engines is significant. Trap devices for filtering the particulates from the exhaust gases are known. One form of trap device includes a ceramic element which may be segmented or not, for providing filtration of the exhaust gases. Another form of trap device includes filter cartridges. In this latter form, cartridges have been disclosed having heaters of various forms, including a ring, a rod, a slotted tube, etc. Known cartridges include the elements of a heater, a filter media, and adequate support for them. The present invention is directed to filter cartridge technology and is distinguished in that improvements to the basic form of a filter cartridge are presented to better conserve heat and to increase heater longevity.